In a vehicle having a gasoline/electric hybrid transmission, the vehicle may be powered alternately by a gasoline-powered internal combustion engine or an electric motor to thereby optimize fuel efficiency while reducing vehicle emissions. Hybrid vehicles achieve their relatively high fuel efficiency in large part by alternating between the gasoline-powered engine and the electric motor when one power source is better suited than the other for a specific vehicle operating condition. For example, a gasoline-powered engine is known to be more efficient than an electric motor during periods of constant or relatively non-variable vehicle speed, such as while cruising at a sustained rate of speed, while an electric motor is generally better suited than a gasoline engine for use when the vehicle power requirements are highly variable, such as during starting or stopping of the vehicle.
Vehicles having either conventional internal combustion or hybrid gasoline/electric transmissions typically utilize a torque-transmitting device known as a friction clutch or clutch pack for smoothly engaging or coupling two rotating bodies or shafts to transmit torque therebetween. Likewise, the same clutch pack is used to subsequently disengage the coupled shafts to interrupt the power transfer and permit, for example, a smooth shifting between the various gears of a planetary gear set and/or decoupling of one or more motor/generators. Hybrid vehicles in particular generally shift gears in a more controlled and synchronous manner relative to conventional gas engines, due in part to the unique configuration and integrated hybrid motor and transmission controls. However, even within the more synchronous shifting mechanism of a hybrid transmission, conventional clutch packs tend to require a higher hydraulic pump pressure to quickly and fully actuate the conventional clutch-apply mechanism, which may in turn lead to higher losses within the hydraulic circuit and/or spin losses at or along the clutch plate interface.